Chain Tensioner with Resilient Ring for Noise Reduction
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Solution Overview
Problem
Existing chain tensioners generate rattling noises on engine start-up due to excessive plunger retraction and excessive noise from seizing during normal operation, with complex designs and increased manufacturing costs.
Innovation Solution
A chain tensioner with a resilient ring and annular rack teeth, where the resilient ring is radially expansible and contractible, allowing controlled movement of the plunger to prevent seizing and reduce noise, and a downsized design with adjustable inclination angles for optimal operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If a ratchet mechanism with concave grooves and groove-engaging member is provided to restrict plunger retraction on engine start-up, then rattling noise is reduced, but the plunger may seize during normal operation due to excessive chain tension
Solution Approach 1:
The resilient ring provides dynamic, position-dependent control of plunger retraction. During engine start-up, the ring engages the steeply sloping rear side of rack teeth to restrict retraction and reduce rattling noise. During normal operation, the ring can slide along the gradually sloping front side of rack teeth, allowing controlled retraction to prevent seizing while maintaining adequate tension.
Solution Approach 2:
The ratchet mechanism uses two distinct slope angles on rack tooth surfaces to provide different functional characteristics. The steeply sloping rear side (first slope) restricts plunger retraction during start-up to eliminate rattling noise, while the gradually sloping front side (second slope) allows controlled retraction during normal operation to prevent seizing.
2Reliability
If predetermined backlash is provided in the ratchet mechanism to prevent plunger seizing, then seizure is reduced, but the amount of rattling noise on engine start-up increases
Solution Approach 1:
The resilient ring creates a dynamic system where the effective backlash varies with operating conditions. During start-up, the ring's engagement with the steeply sloping rear side of rack teeth minimizes effective backlash, reducing rattling noise. During normal operation, the ring can move along the gradually sloping front side, increasing effective backlash to allow controlled retraction and prevent seizing.
Solution Approach 2:
The rack tooth profile is segmented into two distinct functional zones: the steeply sloping rear side for noise reduction during start-up, and the gradually sloping front side for seizure prevention during normal operation. This segmentation allows each zone to optimize for its specific function without compromising the other.
3Reliability
If a pawl mechanism is used to engage ratchet teeth, then plunger retraction is restricted, but the overall size of the tensioner increases and installation becomes more difficult
Solution Approach 1:
The resilient ring is integrated directly into the plunger assembly, merging the ratchet engagement function with the plunger structure. This eliminates the need for a separate pawl mechanism that would extend outside the tensioner housing, thereby reducing overall tensioner size and simplifying installation while maintaining reliable plunger retraction control.
Solution Approach 2:
The resilient ring is nested within the plunger-accommodating hole and engages with rack teeth on the plunger surface. This nested configuration keeps all ratchet mechanism components contained within the tensioner housing, eliminating external protrusions and reducing the overall volume of the moving object.
4Stability of the object's composition
If the forward surfaces of rack teeth have a gradual slope with constant angle of inclination, then the resilient ring expands uniformly, but the plunger does not advance smoothly and flip-flop noises are generated
Solution Approach 1:
The forward surface of the rack tooth is designed with a convex curvature instead of a constant angle slope. This changes the geometric parameter along the engagement path, creating variable instantaneous contact angles that promote smooth, continuous ring expansion and eliminate the flip-flop noise caused by uniform gradual slopes.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution eliminates 'flip-flop' noises, ensures smooth plunger movement, prevents seizing, and reduces manufacturing costs by simplifying the ratchet mechanism and allowing easy installation and maintenance.
Implementation Method 1
a resilient ring which is radially expansible and contractible between a radially contracted condition and a radially expanded condition
Implementation Method 2
The plunger is urged in the protruding direction by a plunger-biasing spring
Implementation Method 3
Movement of the plunger in the retracting direction is controlled by hydraulic damping effected by leakage of oil through a restricted space between the outer peripheral surface of the plunger and the cylindrical inner wall of the plunger-accommodating hole
Data Source
AI summary
In a tensioner having a ratchet mechanism composed of annular teeth on a plunger and an expansible resilient ring disposed in a groove formed in the inner peripheral surface of a plunger-accommodating hole in a tensioner housing, the rear surfaces of the annular teeth have a steep slope, and the front surfaces of the annular teeth have a gradual slope with a convex curvature such that the rate of change of the slope decreases proceeding in the direction of retraction of the plunger.